The invention is directed to a method and to an arrangement for fine area correction of color images. This method is also known under the names of selective or partial color correction or retouch. A system for selective color correction and color recognition is already disclosed by Published Great Britain Application GB 2117902. Here, an operator can move a cursor back and forth on a color image that is displayed on a monitor. For correcting a specific color of the image, the cursor is brought to a picture element that corresponds to the color to be corrected and the corresponding color coordinates or color values are stored. In order to reduce errors in the color selection, picture elements from the environment of the selected picture element are also taken into consideration. Further, samples can also be taken in the dark and in the bright area of the color in order to also be able to take dark and bright areas of the color into consideration in the color correction. The result may be seen in FIG. 1. Here, the colors are shown in the LAB color space. Analogous to the luminance of the samples that have been taken, a plurality of planes result in the L*-axis in which the individual samples are contained. The centroid of the samples is now identified for each of these planes and the points acquired in this way are connected with a curve I. In order to also allow color deviations from the curve I, color values are also taken into consideration that lie at a defined distance or in a defined tolerance region r from the curve I. The result is a three-dimensional color space that contains the color to be corrected. Colors that lie outside the color space are not corrected. A disadvantage of this method is that the color space is designed rotationally-symmetrically relative to the I curve, so that an arbitrary shaping of a color correction area is not possible, and colors that are actually also to be corrected are thereby not covered. A solution of this problem would be comprised in enlarging the tolerance region r; this, however, leads to the fact that colors at other locations in the color space are then also covered which are not to be corrected.
Another possibility for selective color retouch is comprised in placing a mask (also often referred to as a "lasso") around a color in the image to be corrected, as shown in FIG. 2. An area in the image that contains the selected color is traced with the cursor and a geometric mask is thus generated. The color correction then acts only on the area inside the mask. The problem of this method is that extremely bright or extremely dark regions are also co-covered. This can lead to an over-correction of the dark or bright locations, this being noticed in the color-corrected image as disturbing color spots. Further, the demarcation of the area in the image or the generation of the mask must occur extremely precisely since the entire color area in the image is otherwise not covered, or an adjoining color is also covered which is not supposed to be corrected. This then leads to color discontinuities at the locations in the image where different colors abut one another.